Telephone call distributing system



Jan. 16,v 1940. I w, T, PQWELL, 2,187,174

` TELEPHONE CALL DISTRIBUTING SYSTEM Filed Mrcn :51, 193e 5 sheets-sheet 1 W4 I Y a9 aaa @ab asc asd 50 /NcaM//vs Til/Nxs 39 39 3% as 39 d marre-,es

a9 39a au asc a9 d as asa asa asc 39d INVENTOR, wmFlzED T. PowELL ATTORNEY.

Jan. 16,Q 1940.J we T. POWELL TELEPHONE CALL DISTRIBUT-ING SYSTEM' 5 Sheets-Sheet 2 Filed March 31, 1938 INVENTOR.

WINFRED T. POWELL ATTORNEY.

Jan. i6, 1940. w. T. FowELa.

TELEPHONE CALL DISTRIBUTING SYSTEM Filed March 31. .1958

5 Sheets-Sheet 3 j 1NVENTOR. Y

' WINFRED 'l'. POWELL ATTORNEY.

Jan. 16, 1940. w. T. lPowELl.

TELEPHONE. GALL DISTRIBUTING SYSTEM Filed March 31, 1958 Sheefcs-Sheel;l 4

[lll 1NVENT0R wlNFszED T. POWELL ATTORNEY.

d .1m16,194o. W,`T,POWEL, 2,157,174 A I TELEPHONE CALL DISTRIBUTING SYSTEM 5 Sheets-Sheet 5 Filed March 5l, 1958 www.

, MELE@ INVENT OR.

WINFRED T. POWELL` BY 9 www ATTORNEY.

I Patented Jem. 16, 1940'l t l 'y .UNITED- STATES PATENT OFFICE t' p 2,187,174 t l i i.

TELEPHONE `CALL DrsrRrBU'rING SYSTEM y Winfrea T. Powell, Rochester, N. Y., assigner te The Stromberg-,Carlson Telephone ManufacturingV Company, Rochester, N. Y., a'corporation of New York Application March 31, 193s, serial No. 199,203 l 9 Claims.`

kment, however, has for its purpose the reduction of the number iof switching devices necessary in distributing callsto different operators positions in such a system.

The lvarious features and advantages of the invention will appear from the detailed descrip' tion and the claims when taken with the drawings in whichFig. `1 is a diagrammatic showing of the grouping of a small portion of the present system in which there is illustrated two groups of incoming trunks and a group of outgoing trunks arranged to be inter-connected by finder switches under the control of certain` allotters and extended starter wire circuits, Figs. 2 and 3, when arranged in the order named, and with Figs. 4 and 5 placed below Fig. 3 in the order named, diagrammatically represent a portion of a telephone system utilizing the present arrangement.

The present invention is applicable to the distribution of calls in a telephone system of any size but for the purposes 'of this description, it is assumedthat there are 400 A or incoming trunks similar to that shownin part in the upper righthand corner ofiFig. 2. These incoming trunks l e are arbitrarily divided into eightgroups each comprising 50 trunks, each of which trunks terminates on a` wellr knownintermediate distributing frame (not shown). There are also provided 240 B or outgoing trunks, a portion of one of said B trunks being illustrated in the upper righthand part of Fig. 3.l Each of the B trunks is provided with a'iinder switch of the so-called stay-put type, each nder switch being provided'with multiple terminals in which 50 incoming trunks terminate. The 240B trunks (with their 240 finder switches)4 are arbitrarily divided into six` groups to terminate at six B operators positions.

` For th'epurpose of assigning idle i'lnder switches for/use, thereare provided 40 stay-put allotter switches, one `allotter switch being individual to a group of ten incoming trunks. Each allotter is preferably provided with 24 sets of terminals, but

since there are only six B operators positions common tothe allotters,fonly six points or sets of terminals in the allotter are necessary for effecting allottment of trunks. Howeventhe six mentioned points can be repeated four times throughoutthe terminal bank Q f the allotter switch, by properly connecting the sets of termiy e nals fin multiple. Since each of the 40 outgoing trunks at each of the 6 B operators positions is equipped with a finder bank, the iifty sets Aof terminals of each of the finders can be connected at the intermediate ,distributing frame so that f the nrst five iinder switches at each of the six B operators positions, or a total of thirty finder switches, have access to the'rst group of fifty incoming trunks. f

l In Fig. 1 there is illustrated two typical groups of fty incoming trunks (represented by single lines), each of which groups is arbitrarily divided into subgroups of ten trunks each withan allote ter forv assigning trunks in each subgroup, making a total 'of 'live allotters for'the group. There is also illustratedin this gure, live outgoing trunks, individualto eachof the six B operators positions, or a'total of thirty outgoing trunks. For example, if any lincoming trunk in the first subgroup cf ten is taken for use by an A operator, a nder individual to an outgoing trunk in therst group of such trunks will be started if the #1 allotter is standing in position l as illustrated in Fig. 1. The particular one of these five nders of the rst group is determined bythe busy or idle condition of these nders. It will be understood thatthe allotti'ng of the ve nders in this group isy determined by the extended starter wire circuit controlled by relays such as 39 (Figs. l and 3). The energization of aarelay 39 continues during the time that its Afinder is inuse so thatthis relay disconnects the startingcircuit'from its finder,yn0w busy, and extends it to the nextidle finder of the group. It Will be seen from this arrangement that an allotter in each otits six f positions allots'for use a group of ve outgoing trunks inv each of its six possible settings and that an extended starter wire functioning in conjunction with the allotter, allots for use an idle outgoing trunk and its finder switch in this group of ve outgoing trunks.

- It is believed that the-'invention will` best be understood by describing` the operations involved in establishing a telephone connection from a calling subscribers station designated A to` 'a B operators position at a distant oiiice. When the subscriber at A initiates va call by removing his receiver from its switch hook, the line relay 5 is energized from ground and grounded battery,

respectively, through its-two-windings in series, armatures and back contacts 'of the cut off relay `l over the two sides :of the calling line and through the substation circuits. yThe line relay 5 when energized completes a circuit, at its arma- EIl) son.

ture and front contact, for lighting the line lamp l. An A operator at the office where the calling subscribers line terminates, notes the lighting of this lamp and inserts the plug P of an idle cord circuit at her position, into a jack J associated with this lighted lamp. With the cord circuit thus connected to the calling line, the answering supervisory relay 8 is energized over the answering portion of this cord circuit and over the calling subscribers line in series. The operation of the supervisory relay 8, at its armature and back contact, opens a break point in the circuit of they supervisory lamp 9. Also when this cord circuit is connected to the calling line, the cut off relay 6 of this line is energized from ground, winding of this relay, sleeve contacts of the jack J and plug P, winding of the relay IQ to grounded battery. The cut ott relay 6, at its armatures and back contacts, opens the energizing circuit of the line relay 5 which deenergizes to extinguish the line lamp l'. The relay 0, when energized, closes a break point in the circuit of the supervisory lamp 9, but this lamp does not light at this time since its circut is interrupted at the supervisory relay 8. The operator now depresses the listening key K to connect her telephone set T to the cord circuit taken for use and thereupon inquires for the designation of the wanted subscriber.

Let it be assumed that the incoming trunk, a portion of which is shown in the upper right hand corner of Fig. 2 connects to the wanted office where the wanted subscribers line terminates. The operator then inserts the plug P of the cord circuit that has been taken for use, into the jack J of the mentioned trunk. Current is thereupon connected to the trunk by way of the calling supervisory relay il, from grounded battery, its right hand winding, ring conductor of the cord circuit, ring contacts of the plug P and jack J inner armature and back contact of relay i2, left hand, high resistance winding of the relay I3, outer back contact and armature of relay I2, through the tip contacts of the jack J and plug P', tip conductor of the cord circuit, left hand winding of the supervisory relay II, to ground. The supervisory relay is not energized in this circuit because of the high resistance of the left hand winding of relay Iii. Relay I3 is energized over this circuit. Also on the insertion of theplug P into the jack J', the relay i5 is energized from grounded battery, Winding of relay I5, sleeve conductor of the cord, sleeve contacts of the plug P' and jack J Winding of the relay IS to ground. The energization 'of the relay I5 closes a break point in the lighting circuit of the supervisory lamp I4.

With the relay I3 operated, an allotted finder is started to extend the selected trunk to an idle trunk at an idle B operators position at the wanted office. rIhis operation is initiated by the closing of a circuit from ground at the inner armature and back contact of relay i8 (common to the group of fifty incoming trunks), armature and front contact of relay I3 now energized, winding of relay I9, its continuity spring and back contact, conductor 2i), uppermost back contact and armature of slow releasing relay 2i, armature and back contact of relay 22,l armature, back contact and winding of the allotter stepping magnet 23 to grounded battery. The stepping magnet 22 is not energized in this circuit owing to the high resistance of the relay I9. The relay i :l however, is energized in this circuit and closes a locking circuit for itself from ground at the armature and back contact of the relay I8, armature and front Contact of relay I3, winding of the relay 22, armature, back contact and winding of the stepping magnet 2- to grounded battery. The relay 22 is energized in this last described circuit and at its inner armature and back contact, opens the circuit including the conductor 2t so that no other relay of the other ten incoming trunks of this group can be operated at this time. However, the relay 22 at its lowermost armature and front contact closes a circuit for advancing the four other allotters of this group away from the preselected position so that these other allotters preselect other finders for the remaining incoming trunks of this group. rlhis is effected in a circuit completed from ground, front contact and lowermost armature of relay 22, inner armature and back contact of relay 2I, allotter brush 25, in

' its first position, armature 26a and back Contact of relay 2F, conductor 2l, back contact and armature Ziib of relay 26, allotter brush 2S ofthe number 2 allotter, back contact and inner armature of relay 3l, middle armature and baci: contact of relay 22a, armature, back contact and winding of the stepping magnet 3B of the number 2 allotter to grounded battery. The stepping magnet ci this number 2 allotter advances the allctter brush 29 to preselect an idle finder for other incoming trunks. Likewise, the stepping magnet 32 of the number 3 allotter is also energized from grounded battery, winding of the stepping magnet 32, its back contact and armature, back contact and middle armature of relay 22h, inner armature and back Contact of slow-releasing relay 33, allotter brush 3.4, armature 2Go and back contact of relay 25 and thence over the conductor 2l and the remainder of the circuit previously described to ground ai tizie middle armature and front contact of relay 2 the stepping magnets of the number 4 and of the number 5 allotters (not shown), as well as all other allotters of other groups which may be standing in position 1.

Also with the relay 22 energized, a circuit is closed from ground, lowermost front contact and armature of relay 22, conductor 35, number l allotter brush 36, conductor middle armature and back contact of relay 38, winding of the slow-releasing relay 39 to grounded battery for starting the allotted finder to hunt for the incoming trunk to which the call has been extended by the A operator. At the inner upper armature of relay 33, the conductor 4d included in the chain or extended starter wire circuit to other B operators positions of the group, is opened. Howeven at the uppermost armature of the relay 39, a circuit is closed from grounded battery, winding of the slow-releasing relay 4I, uppermost front contact and armature of relay 33, continuity spring l2 and back contact of the relay 4I to ground. The slow-releasing relay III is energized and closes a substitute energizing circuit for itself from grounded battery, its winding, uppermost front contact and armature of relay 3S, continuity spring l2 and middle armature of relay l, lower winding of the differentially wound relay 43, innermost back contact and armature oi this relay, iinder test brush 44 and thence successively over conductors such as Li, armatures and back contacts of relays similar to IE), back contacts and armatures of relays similar to the cutoff relay I2, to ground. In this connection it will be understood that all trunks except the incoming trunk illustrated, will be Similar stepping circuits are completed for V characterized by a groundv potential on their test a circuit traceable from grounded battery, its

winding, armature and back contact, uppermost front contact and armature of relay 4l, innermost back Contact and armature of relay 45, :nder test brush 54 and thence to ground, as previously described, at the armature andback contact of relays similarv to` cut oilrrelay i2. When the test brushg44 encounters the test terminal 41 of the incoming trunk taken for use, this terminal will be characterized by the absence of ground potential, since this ground potential is now removed at the outer armature and back contact of relay I9. As soon asv the iinder test brush 44 encounters the test terminal 41 of the mentioned incoming trunk, the circuit to ground through the lower winding of the relay 43 will be interrupted and the switching relay 43 will be energized in the circuit previously described as including its upper winding. With the relay 43 energized, the operatingcircuit for the stepping magnet 46 of the iinder will be interrupted at the innermost back contact and armature of the switching relay 43 so that the finder brushes 49, 50 and 44 will no longer be advanced. At the innermost armature and front contact of the relay 43, ground potential `is applied through vthe test brush 44 to the test terminal 41 of the selected trunk to render it busy. As soon as the switching relay 53 is energized, a circuit is completed' for energizing the cutoff relay l2 of the selected incoming trunk. This circuit extends from grounded battery, Winding of the cutoi relay l2, outer front contact and armature of relay I9, sleeve conductor 45, test terminal 41, finder brush d4, armature and front contact of switching relay 43 to ground. The cutoff relay i2, when thus energized, closes a locking circuit for itself through its inner frontk contact and armature and thence over the re-V mainder of the circuit previously described as extending to ground, at the' innermost armature and front contact of switching relay (i3. Also 4as soon as the cutoi relay i2 is energized, it opens the original operating circuit of the relay i3, so that this relay releases and at its armature and front contact opens the energizing circuit of the relay I9 (Fig. 2) and 22 (Fig. 4l) which it will -loe recalled are energized inl series. Relays I9 and 22 release. I

Also with the relay 43 energized, the relay at the selected operators'position is energized over the two sides ofthe allotted trunk through the nder brushes 49 and 59 and the two sides of the selected trunk, thence through the tip and ring contacts of the jack J and plug P', both windings in series of the supervisory relay li,

to ground and to grounded battery respectively When the relay i3 is energized, it closes at its armature and front contact, an energizing cir-- cuit for the slow-releasing relay 5i On the operation of the relay 5i, the relay 3S has its operating circuit completed. When the relay 33 operates to attract its armatures, it interrupts, at its middle armature and back contact, the ener gizing circuit for the relay 39 which deenergizes.` With the middle armature and. front contact of relay 38 closed and with the relay 39 deenergized, the chain or extended starter wire circuit including the conductor is completed, which' starter circuit is extended to allot the next outgoing trunk to this B position. AAt the lower most armature and front contact of the relay 38,

a circuit is completed from ground, conductor 52,

lower winding of the relay 26 to grounded battery, Relay 25 at its armature and front contact applies ground to the test terminal of the number l allotter, with which test terminal the brush 25 ofthe number 1 allotter is in engagement, I

so that the remaining allotters of this group cannot preselect the B operators position now in use. It will be appreciated that the stepping magnet 25 of the allotter with its brushes shownv at 25 and 35 are nowA stepped away from this position because the operating circuit of the stepi ping magnet 23 is completed at the middle arma-y ture and back contact of the relay 22, brush 25 and front contact 26a of relay 26 to ground.

As soon as the slowreleasing relay 39 (Fig. 3) is energized, it completes a circuit from ground at its lower armature and front contact, conductor 5d, winding of the slow releasing relay 51 to grounded battery. This slow releasing relay is thus energized and at itsl armature 51b and front contact, closes a circuit from ground, con-I ductor 52, back contact and armature 26a to the test terminal 53` of the allotter so that all of the allotters areprevented from stopping in position 1, since B position 1 is busy -handling a call.

When the outgoing vtrunk or B operato-rs cord circuit shown in the upper righthand corner of l-ig. 3 is seized in the manner already described, the relay 54 in the upper right hand corner of Fig. 5is energized. It will be understood that the B cord circuit may be substantially the same as that disclosed in Figs. 6 and 7 of applicants Patent #1,861,754, granted June 7,1932, from which patent it will be seen that las soon as the B cord circuit is selected, the B operator will receive the wanted station designation from the A operator and will complete the connection to the wanted subscriber in the manner therein set forth. 1n the course ofthe extension of the mentioned B'cord circuit to the wanted telephone line, as already indicated, the krelay 5ft of Fig. 5 will operate in the same manner as relay 1l of the mentioned patent. With the relay 54 operated, it closes a circuit at its armature and front contact, right hand winding of therela'y 55 to energize this last-named relay. Relay 55 at its ar` mature 55a and front contact extends a circuit from ground at the armature 56h and back contact of. relay 55, conductor 69, front Contact 55a, and armature of relay 55, front contact 13b' and armature of relay19, and thence over the conductor 52, to the'test terminal 53.0f the allotted position, whereby a busy potential is still main'- tained on the multiple test terminals of the mentioned position at the allotters. When the B. operator has progressed with the extension of the B cord circuit to the wanted line, the relay 54 will be cle-energized for releasing relay 55, so` that the ground potentialy applied to allotter test terminal 53 over the conductor 52 is removed.

The present arrangement affects the distribution of calls one at latirne to the six B operators positions of the group in questionand thereafter an additional call is parked in succession at each ofl these positions awaiting the completion of the original call therealtY The distribution.

ofone call to each of the six operators positions is effected by the extended starter wire arrangement shown in the lower right hand corner of 3. The parking of a second call in addition 'to the original call is effected in the following manner: If all of the six B operators positions in the group are being simultaneously used in the extension of a call, the slow releasing relays l, 53 and 59 respectively associated with these positions, as well as three similar relays of the three other B operators positions, not illustrated, will be energized and then de-energized in the manner already described. Also the relays 55, 55A and 55B, etc, respectively associated with these positions will be energized. This will e1- i ect the energization of the relay 56 which is common to the six B positions of the group in question. The energizing circuit for the relay 55 is traceable from grounded battery, winding of this relay, right hand armature and back contact of relay 59, middle iront contact and armature of relay 55B, right hand armature and back contact of relay 58, front contact and armature of relay 55A, right hand armature and back contact of relay 5l', front Contact and armature of relay 55 tc ground. The relay 55 when energized in this circuit, closes a locking circuit for itself through its right hand front contact and armature, front contacts and armatures of relays 55B, 55A and 55 to ground. Relay 55 when energized also removes ground potential at its back contact and armature 56D from the conductor 69 so that no allotter will be stepped away from the set of terminals including the test terminal 53 and others corresponding thereto.

Let it be assumed that an outgoing trunk or B operators cord circuit at each of theY six B operators positions of the group is simultaneously being extended with the result that the relay 55 (Fig. 5) is energized. Let it further be assumed that six other calls have been extended to incoming trunks for extension by these same six operators. In accordance with the present arrangement a second call is parked at or distributed to each of the mentioned six B operators positions. These mentioned six calls are assigned one to each B operators position by the allotter arrangement (Fig. 4) Each of these second six calls will result in the energization of a relay I9 of the next allotted outgoing trunk of a B operators position. This relay when energized will lock itself operated in series with the relay 22 of the #l allotter. The operation of the relay 22 of the #l allotter will effect the energization of the relay 39 of the allotted outgoing trunk so that its nder switch will seize the incoming trunk to which the call has been extended. The seizure of this incoming trunk will effect the energization in succession of the relays 48, 5I and 38 as previously described. When relay 39 is operated, it will complete a circuit from ground at its lowermost armature and iront contact, conductor 56, udnding of the slow releasing relay 51 of the rst position to battery. Relay 5l, when thus energized, will close a locking circuit for itself from grounded battery, its winding, inner front contact and armature, conductor 68, front contact and armature 56h of relay 55, which is energized because a call is be ing completed at each of the six B operators positions of the group, conductor 59, front contact and armature 55a of relay 55, front Contact and armature b of the induction coil relay 65 (relay 'l0 being energized when the operator is at her position), front Contact and armature Bib of relay 5'! to ground. Thus the relay 51 will remain energized as long as a call is parked at the number l position.

Similarly the second call of the next succeeding six calls will be parked at the second B operators position. This will result in the energization of relay 58, common to the second B operators position. Relay 58 when energized likewise closes a locking for itself from grounded battery, its winding, its inner front contact and armature, conductor 6l, front contact and armature 56o of relay 55, front contact and armature of relay 55A, front contact and armature 62h of the induction coil relay 52, front contact and armature 58h of relay 58 to ground.

In like manner, the relay 59, individual to the third B operators position is operated and locked as well as similar relays of the three remaining B operators positions (not shown in Fig. 5) of the group. With all of these relays such as 5l, 53, 59 etc. locked operated, the relay 53 common to the six operators positions of the group will be energized from grounded battery, winding of relay B3, front contact and armature 55a of relay 5S, front contact and armature 55a oi relay 5S, front contact and armature 58a of relay 58, front contact and armature Sla of relay 5l to ground. Relay 63 is thus operated and at its armatures and front contacts it closes circuits for operating all of the allotter lock out relays, such as relays 2l, 3| and 33. These lock out relays prevent unnecessary hunting by the allotters and also prevent the operation of any relay such as i9 of any trunk attempting to call under this condition of all positions locked. The circuit for the illustrated group of allotters is traceable from ground, the outermost armature and front contact of relay 63, conductor G4, lower windings of the slow releasing relays 2l, 3l and 33 tc grounded battery. Also the two other relays, respectively individual to the two remaining allotters of this group (not shown), are energized in multiple over the conductor 84. With these relays energized, the circuits for energizing each relay such as I9 individual to each incoming trunk is opened so that no more calls can be distributed to the B operators positions of the group, It should be pointed out that when the relay 2l is energized it closes a circuit from ground at its lower front contact and armature, conductor 65. upper winding of the relay 3l to grounded battery. Similarly, with the relay 3l operated, a like circuit is completed for energizing the upper winding of the relay 33. By this arrangement the relays 2l, 3l, 33 etc. will be de-energized in succession, thereby insuring that the associated allotters will not be brought back into service at the same time, with the consequent danger of allowing two or more waiting calls to be allotted to the same trunk or position.

Similarly, when all of the rst ve trunks at each of the B operators positions are in use, the relays such as 26, 55, 6l, etc., respectively individual to these positions, will be energized and a circuit will be closed from ground through their uppermost armatures and contacts, conductor 58, winding of relay i8 to grounded battery. Relay |8 at its upper armature applies a busy tone to the line conductors of the incoming trunks by inductive action of relay 3, so that the A operator, taking one of these trunks, knows it has no available outlet. At the inner armature of relay l8, ground is removed from the multiple circuits including the relays l5 so that these relays are rendered inoperative under the conditions assumed. At the lowermost armature and front contact of relay I8 ground is applied over conductor 64 for energizing the relays 2i, 3l and 33 etc. which likewise disables the stepping magnets y said lines, said switches being arranged in groups,

an allotter switch for assigning groups of automatic switches, and means including an extended starter wire arrangement for assigning for use a certain automatic switch in the assigned group.

2. Ina telephone system, a plurality of incoming lines, a plurality of groups of outgoing lines, means including automatic iinder switches for interconnecting said lines, said switches being arranged in groups, an allotter switch individual to each group of outgoing lines for assigning groups of automatic switches, each allotter being provided with related circuits, and means including an extended starter wire arrangement cooperating with the circuits of certain allotters for assigning for use a certain automatic switch in the assigned group.

3. In a telephone system, a plurality of groups of incoming lines, a plurality of groups of outgoing lines, an automatic switch individual tol each outgoing line for connecting the same to any of said incoming lines, an allotter switch individual to each group of incoming lines for assigning a group of automatic switches for use, and an extended starter wire arrangement for each group of outgoing lines and serving to assign for use an idle automatic switch in the assigned group.

4. In a telephone system, a plurality of groups of -incoming lines, a plurality of groups of outgoing lines, an automatic switch individual to each outgoing line for connecting the same to any of said incoming lines, an allotter switch individual to each group of incoming lines for assigning va group of automatic switches for use, an extended starter wire arrangement for each group of outgoing lines and serving to assign for use an idle automatic switch in the' assigned group, means for rendering said allotter switches inoperative when all of said outgoing lines are in use and means for rendering said allotter switchesl operative in succession when any of said outgoing lines are released for use.

5. In a telephone system, a plurality of groups of incoming lines, a plurality of groups-of outgoing lines, an automatic switch individual to each outgoing line for connecting the same to any of said incoming lines, an allotter switch individual to each group of incoming lines for assigning a group ofy automatic switches for use, each of said allotters being provided with a stepping magnet, an extended starter wire arrangement for each group of outgoing lines and serving to assign for use an idle automatic switch in the assigned group, a series of relays, one of said relays being associated with each allotter switch for rendering the stepping magnet thereof inoperative, means for operating each relay when all outgoing lines are unselectable, and means for maintaining operated each relay except the lrst in the series, at the preceding operated relay in the series.

6. The method of distributing calls from a group of incoming lines to a group of operators positions, which method comprises distributing a call to each .position till all of said positions are engaged in extending a call, directing a second call only to each position, cutting in a second call to the position to which it has been directed as soon as the iirst call at said position has been extended, and rendering said groups of incoming lines busy while an assigned call is awaiting cutting-in at each position of the group.

"7. In a. telephone system, groups of interoliice trunks, a group of finder switches associated with each of said interofce trunk groups, a plurality of operators, positions, a group of incoming trunks at each of said positions dividing into subgroups, the incoming trunks of separate subgroups of a position being associated with iinder switches of separate groups, allotter means controlled over said interofce trunks for allotting idle operators positions, an idle sub-group of the idle position and an idle trunk of the idle subgroup, and means controlled by the busy condition of a plurality of said operatorspositions for permittingsaid allotter means to allot an idle sub-group and an idle trunk therein at a busy position.

8. In a telephone system, groupsk of interoice trunks, a group of finder switches associated with each of said interoice trunk groups, a plurality of operators positions, a group of incoming trunks at each of said positions divided into subgroups, the incoming trunks of separate subgroups of a position being associated with nder switches of separate groups, and allotter means controlled over said interolice trunks for allotting idle operators positions, an idle sub-group of the idle position and an idle trunk of the idle sub-group.

9. A telephone system including incoming lines, cord circuits at operators positions, nder switches associated with said cord circuits capable of connecting said cord circuits to said incoming lines, means controlled over said incoming lines for allotting idle cord circuits at an operators position and connecting said cord circuits 

